I think it's all about the possibility to later upsell. I don't think the economics work out where it's cheaper to install something like a seat heater in every car and permanently disable for price discrimination purposes (the way you might for e.g. a CPU).
My brain can kind of rationalize this as "it makes the up-front price lower, and you can add features to your car without even visiting a dealer", but my heart definitely recoils at the idea of paying for something like that already in my possession.
I agree that it feels really wrong but I don't think it is actually unethical to lock features like this. (Although the way the locks are implemented may be unethical.)
It allows making multiple logical models with a single production line. This lowers the cost and in theory that is valuable to consumers. I imagine that if there was no ability to "upgrade" later this wouldn't even be news. Consumers would just see it as a base model and a premium model, and Tesla found a very cost effective way to provide two models of car. Or four models if you count self-driving.
But upgrading later is actually valuable. Why not let someone add features as their budget allows? It does "expose" that these are only software locks but I think that is actually fine. In theory it is just the people who purchase the premium upgrades that are paying for these features in all cars. It shouldn't necessarily affect the price of the base model and you aren't really paying for the feature unless you purchase the upgrade.
My brain can kind of rationalize this as "it makes the up-front price lower, and you can add features to your car without even visiting a dealer", but my heart definitely recoils at the idea of paying for something like that already in my possession.